what temperature setting for how long?

I've bought a few lp's on ebay, with mostly bad results, but thought this one was more interesting than most. I bought a "sealed" lp of Chopin polonaises from christofori 383, which came pretty warped. I told him about the problem. He responded the same day, saying that (1) since it was sealed he could not know it was warped (seems reasonable) and (2) I should put it in an oven set low for a few minutes (did not say how low or for how long - I guess these recipes necessarily vary according to the strength of the ingredients). My question is what temperature setting for how long do you recommend for Chopin, and how many times do you baste?